Speciation study of the anti-inflammatory drug tenoxicam (Htenox) with Cu(II): X-ray crystal structure of [Cu(tenox)(2)(py)(2)]center dot-EtOH

摘要

A speciation study was carried out in aqueous solution of the anti-inflammatory drug tenoxicam (Htenox), under quasi-physiological conditions (temperature of 37 degreesC and ionic strength 0.15 M NaCl) in order to determine the acidity constants from spectrophotometric studies, the pK(a) values found being pK(1) = 1.143 +/- 0.008 and pK(2) = 4.970 +/- 0.004. Subsequently, the spectrophotometrical speciation of the different complexes of Cu(II) with the drug was performed under the same conditions of temperature and ionic strength, observing the formation of Cu(Htenox)(2)(2+) with log beta(212) = 20.05 +/- 0.01, Cu(Htenox)(2) with log beta(012) = 13.6 +/- 0.1, Cu(Htenox)(2+) with log beta(111) = 10.52 +/- 0.08, as well as Cu(tenox)(+) with log beta(011) = 7.0 +/- 0.2, all of them in solution, and solid species Cu(tenox)(2)(s) with an estimated value of log beta(012)(s)approximate to18.7. The crystalline structure of the complex [Cu(tenox)(2)(py)(2)](EtOH)-Et-., was also determined, and it was observed that tenoxicam employs the oxygen of the amide group and the pyridyl nitrogen to bond to the cation. (C) 2003 Elsevier Science Inc. All rights reserved. [References: 64]